For marketing and other reasons, manufacturers of radio communications devices typically offer several different configurations for each "model" of communications product manufactured. A particular model of mobile radio transceiver may have a "basic" or minimal configuration but may optionally be provided with additional features at additional cost.
For example, a basic transceiver configuration may provide communications over a limited number of communications channels for basic radio transmitting and receiving functions required by all users. Some users may, however, have additional requirements requiring additional features--such as additional communications channels, receiver channel scanning, telephone access (DTMF) capability, etc. The ability of a manufacturer to provide such additional features increases the flexibility, versatility, desirability and range of applications of the product without penalizing purchasers of the basic configuration with increased cost. Purchasers of the basic model pay a minimum price for the minimal configuration, while users requiring additional features pay an increased price based on the number and type of options they require.
In the past, additional features were generally provided by incorporating additional components and circuitry into the transceiver. For example, channel scanning capability or additional operating channels were added by installing additional frequency selection circuitry. Similarly, DTMF (TOUCH TONE) capability required an additional tone generator circuit and associated keypad to be installed. Transceiver designers used modular architectures to accommodate additional plug-in modules.
An example of this design approach is the prior art "MLS" series radio transceivers manufactured for General Electric Company by Japan Radio Corp. These "MLS" transceivers include basic transceiver circuitry disposed within a housing. The front panel assembly of the transceiver housing is manufactured separately, and consists of a separable front panel "escutcheon" plate. Mechanically mounted to the escutcheon plate is a printed circuit board which plug-connects to the basic transceiver circuitry when the escutcheon plate is mechanically fastened to the housing. The escutcheon plate and associated printed circuit board thus comprises a module separable from the transceiver main housing and basic circuitry, this module including user controls, circuitry required to connect the user controls to the transceiver circuitry, and additional circuitry needed to perform the additional functions.
Since additional features in many cases require different additional user controls, different models of escutcheon plate modules were produced for the "MLS" series transceivers. In particular, the "MLS" transceiver was made available in several different versions, such as: (1) a two-channel "basic" version; (2) an 8-channel version with scan feature; (3) a 16-channel version without scan; and (4) a 16-channel version with scan feature. Different interchangeable escutcheon plates with different user control arrangements corresponding to these different transceiver versions were provided. The particular escutcheon plate/control panel installed on a particular "MLS" transceiver limited the transceiver features the user could access. For example, the escutcheon plate corresponding to the "MLS" transceiver version with 16-channel capability and no scan feature does not have a control to actuate the scan feature--preventing the user from obtaining the benefit of the scan feature. Similarly, the escutcheon plates corresponding to the 8-channel transceiver versions do not include user controls to access more than 8 channels.
Since all "MLS" transceivers included identical basic transceiver circuitry and main housing, reduced manufacturing costs and increased reliability derived from large scale manufacturing were obtained. Specific purchaser selected additional features could be provided in a particular unit simply by installing the appropriate escutcheon plate module--a procedure which could be performed in the field or at the distributor if desired. Incorporation of the circuitry performing the additional functions and user controls interacting with such circuitry within the same front panel escutcheon plate module permitted a transceiver to be reconfigured by simply "unplugging" one module and "plugging in" a different module (further increasing reliability and decreasing manufacturing costs).
Digital microprocessor controlled radio communications devices such as the "MLS" series transceiver are generally known, of course. The following is a (by no means exhaustive) listing of prior patents and publications generally relevant to the state of the art of so-called "digital radios":
U.S. Pat. No. 4,378,551--Drapac PA0 U.S. Pat. No. 4,392,135--Ohyagi PA0 U.S. Pat. No. 4,525,865--Mears PA0 U.S. Pat. No. 4,247,951--Hattori et al PA0 U.S. Pat. No. 4,254,504--Lewis et al PA0 U.S. Pat. No. 4,510,623--Bonneau et al PA0 U.S. Pat. No. 4,688,261--Killoway et al PA0 U.S. Pat. No. 4,618,997--Imazeki et al PA0 U.S. Pat. No. 4,771,399--Snowden et al PA0 U.S. Pat. No. 4,484,355--Henke et al PA0 U.S. Pat. No. 4,555,805--Talbot PA0 U.S. Pat. No. 4,638,120--Herve PA0 "DYNA T-A-C 6000X Universal Mobile Telephone", Motorola (1984) PA0 Groh, "The uP: The Key to an Advanced Frequency Synthesized HF SSP Amateur Radio Transceiver", IEEE Transactions on Consumer Electronics Vol. CE-26 (1980).
Such references teach controlling transceiver functions in addition to transceiver operating parameters (e.g., operating frequencies) in response to digital signals stored in a memory device. While older radio transceivers required additional circuitry to perform additional, optional functions such as channel scanning, tone activated squelch and the like, modern digital microprocessor controlled transceivers are capable of performing such additional functions under software control with little or no additional circuitry. For example, receiver channel scanning can be implemented by providing an enhanced receiver program control routine controlling the microprocessor to periodically monitor activity on various channels--and additional frequency data can be stored in a memory device to provide additional transceiver operating channels. Additional tone generating, decoding and control algorithms performed by the microprocessor under control of additional program control software can provide advanced squelch control functions, DTMF and other tone signalling functions, and the like.
It would be unfair (and also poor marketing strategy) to require users needing only a minimal transceiver configuration to pay for the high development cost of advanced features and enhancements. Accordingly, for various reasons it is still very much advantageous to offer the purchaser a "basic" lower cost transceiver configuration while permitting him to select additional features at higher cost--even though the main (and sometimes the only) difference between the basic and the enhanced transceivers may reside in the specific program control routines they execute. This marketing strategy allows the manufacturer to offer the basic unit at reduced cost and at the same time requires purchasers requiring enhanced operation to bear the additional costs associated with developing and providing the additional features. A still further benefit achieved by this strategy is that overall development, manufacturing and inventory costs are reduced substantially--since the same basic hardware configuration can be used for all models of the product.
For this marketing strategy to be successful, however, purchasers of low cost basic transceiver configurations must not be able to easily modify their units to obtain more expensive features. Otherwise, most purchasers would simply buy the "bottom-of-the-line" model and then modify it to obtain additional features (thereby defeating the marketing strategy and also unfairly obtaining the benefit of features for which they did not pay development or licensing costs).
One possible way to prevent purchasers from modifying transceiver units to obtain features they have not paid for is to provide different transceiver configurations, each configuration having essentially the same hardware but including a different PROM (programmable read only memory) storing only the subset of the program control instructions and transceiver parameter data associated with the specific configuration purchased. This approach has several disadvantages, however. Ultra-miniaturization provided by modern manufacturing and packaging techniques now make it possible to inexpensively "pack" hundreds or thousands of components into a very small physical volume (e.g., the interior volume of a hand-held digital radio transceiver). Such assemblies are often extremely difficult, however, to disassemble after they have been assembled at the factory--requiring the appropriate program store memory to be installed at time of manufacture. A large inventory of the various different versions of the program store memory must be maintained, and the final configuration of a particular transceiver must be determined at time of manufacture. It would be highly desirable to somehow defer that configuration determination until closer to time of purchase (so that, for example, distributors would only need to keep one basic unit in inventory).
Commonly assigned U.S. Pat. No. 4,525,865 to Mears discloses an arrangement whereby a non-volatile memory within a mobile radio transceiver can be reprogrammed without physical entry into the transceiver or removal of components to provide the radio with additional operational options (e.g., tone or digital addresses, carrier control timers, or the like). However, if such reprogramming were used to provide optional advanced features, there may be nothing (other than the copyright laws) preventing an intelligent purchaser from downloading upgrade information into his transceiver's internal non-volatile memory. Thus, the Mears solution is highly effective to permit customization of transceiver "personality information", but may have more limited utility in selecting the set of basic operational features to be provided by particular transceivers.
U.S. Pat. No. 4,392,135 to Ohyagi and U.S. Pat. No. 4,378,551 to Drapac listed above disclose security arrangements for enabling and/or inhibiting features in paging receivers.
Ohyagi teaches an "information setter circuit" comprising an 8.times.9 bit PROM in which is stored "option selection bits" for selecting various functional options of the paging receiver (e.g., automatic resetting after an alert, paging by mechanical vibration in lieu of tone, and a battery saving feature). The microprocessor reads the information stored in this circuit as an input to the program control algorithm it executes and enables or inhibits the various option features accordingly.
The Drapac patent discloses discrete logic security circuitry incorporated as part of the pager which connects with option selection circuitry contained in a separable "code plug." The code plug includes circuitry controlling tone decoding, and additional simple fusible link type circuitry which controls selection of various options such as battery saving, automatic reset, and dual call operation. Logic level signals are connected through the fusible links in the code plug to the security logic circuitry, and the logic circuitry in turn enables or disables the various options. The security logic circuitry detects when a user tampers with the code plug fusible link connections and prevents activation of the paging device whenever tampering occurs.
While such arrangements may be satisfactory in the context of a paging device, they do not readily lend themselves to the more complex environment of a full-featured digital radio transceiver--in which many more options may be provided and some additional circuitry and user controls may be required to implement the various options. In addition, greater security than Drapac's code plug can provide is necessary to prevent purchasers from successfully enabling transceiver advanced option features through tampering.
It is also known in certain prior art devices to disable functions by substantially irreversibly modifying circuitry. One example of such a technique is found cable television applications. Some early cable television decoders included multiposition channel selector switches with each channel position corresponding to a different television channel (some of which were categorized as "premium" channels). A subscriber could subscribe to all of the television channels or to only selected television channels (but of course, his monthly subscription fee would be increased if he subscribed to a greater number of "premium" channels). The "premium channels" were transmitted over the cable television network in "scrambled" form (e.g., with suppressed vertical sync signals or with some other essential signal component suppressed or altered) to prevent them from being properly received and displayed by a standard television receiver. The decoder units included a "descrambler" circuit (e.g., a filter/amplifier network for restoring vertical sync or other essential missing signal components) coupled to the multiposition switch.
All such decoder units were shipped from the factory in a standard configuration in which the multiposition switch disabled the descrambler circuit from operating on all channels. However, PC board pathways connected to different switch positions could be cut to prevent the descrambler circuit from being disabled (i.e., to enable the descrambler circuit) at certain switch (channel) positions (thus providing a capability to substantially irreversibly modify the decoder to selectively enable/disable descrambling functions on a channel-by-channel basis). The Cable Television Company could thus "program" a decoder to descramble only the specific premium channels subscribed to by a particular subscriber by opening the decoder unit to access its internal PC board and cutting selected individual PCB pathways coupled to corresponding channel selector switch positions. The decoder was typically housed in a secure sealed cabinet that was difficult or impossible to unseal without using special tools--effectively preventing the average consumer from accessing and severing additional pathways to enable descrambling of additional premium channels.
This technique has now generally been discarded by the cable television industry in favor of periodically digitally downloading channel enablement tables into a non-volatile memory within the decoder and using this channel enablement information to selectively enable/disable descrambling on a channel-by-channel basis. In any event, it is difficult to see how any of these prior art cable television techniques could provide practical solutions to the problem of selecting functions to be provided by digital radio communications transceivers.
It is also generally known to set hardware configurations by selecting continuity/discontinuity between processor-readable connections. For example, it is common for manufacturers of boards for personal computers to include so-called DIP (dual in-line package) switches or jumpers on their boards to allow the user to set parameters (e.g., bus address, interrupt, or the like) associated with the hardware. Such switches/jumpers may in some cases be used to provide information (e.g., "my address is" or "my hardware configuration is") to the processor communicating with the hardware (thus allowing the system to automatically "configure" itself under software control upon power up, for example). Of course, jumpers and DIP switches are designed such that it is easy to change the configurations they select. As a cost-saving measure, some manufacturers may in the past have eliminated the jumpers and/or DIP switches altogether and instead provided PC board pathways the user or installer must cut or scrape off to provide bus address information or the like. These arrangements are often troublesome, however (since a soldering iron is needed to change the configuration once it has been selected) and are therefore typically reserved for the cheapest of devices.
It is unclear how jumpers or DIP switches could be used to specify radio configuration on the hardware level at time of radio purchase while preventing users from later changing the specified configuration. Jumpers and DIP switches are typically relatively easy to set, and are therefore relatively easy to change. Moreover, such devices are normally mounted directly on a printed circuit board or the like--and would therefore require the radio to be disassembled for the jumpers or DIP switches to be set as desired. Thus, this "solution" is similar to the solution discussed above of providing different program store memories for different transceiver versions--and has many of the same disadvantages (e.g., requiring transceiver configuration to be specified at time of manufacture).
The copending patent application Ser. No. 07/183,212 of Ingham filed on Apr. 19, 1988 referred to above provides a highly suitable and successful solution to the problem of configuring a digital radio transceiver subsequent to time of manufacture. In that arrangement, a single "base" transceiver unit is manufactured, this transceiver base unit being common to all of several different transceiver configurations. Different transceiver front panel "escutcheon plates" carrying different control configurations are provided for the different transceiver configurations. These front panel escutcheon plates interconnect both mechanically and electrically to the transceiver base unit.
Thus, the escutcheon plates in the preferred embodiment disclosed in the Ingham application carry entire electrical switch assemblies--including electrical contacts and associated actuator "buttons". The escutcheon plate modules corresponding to all but the "basic" configuration also carry a "security circuit" which communicates with the transceiver microprocessor within the base unit at certain times (e.g., during transceiver "power up"). Different security circuits are provided for the different escutcheon plate configurations, each of the different security circuits permuting signals sent to them in a different way.
In the Ingham arrangement the transceiver sends serial data signals to the security circuit disposed on the escutcheon plate connected to it, and receives back a permuted version of those signals (if the escutcheon plate corresponds to some configuration other than the basic configuration). The microprocessor determines the configuration of the escutcheon plate module in response to which permuted version of the signals it receives back from the security circuit. Thus, the purchaser cannot obtain additional functionality by merely providing additional controls--he must also provide a security circuit corresponding to the new control configuration. Great security is provided against tampering with or defeating of the security circuit because the permutation function performed by the circuit is complex and emulation of this function would require sophisticated techniques and/or a physically large circuit.
While the Ingham arrangement is highly successful in its own right, further improvements are possible. In particular, the escutcheon plates used in the Ingham arrangement are somewhat expensive to manufacture, since they may carry entire electromechanical switch assemblies, electrical connectors, and (for units having "optional" features) an electronic security circuit. It would be highly desirable to provide interchangeable escutcheon plate assemblies comprising only a few mechanical parts. Such a purely mechanical escutcheon plate module design would eliminate the costly (and occasionally unreliable) electrical connectors used in the prior art to connect escutcheon plate modules to transceiver base units.
Unfortunately, the extremely difficult problem arises as to how to prevent a purchaser of the basic configuration version from simply installing different mechanical parts to provide additional features. The problem is that the same features making it possible for the manufacturer or distributor to quickly, easily and conveniently change transceiver configurations also make it possible for purchasers to alter the configurations of their own transceivers (and thus defeat the manufacturer's marketing strategies as well as obtaining "for free" the benefits of advanced transceiver functions and features the purchaser should in all fairness be reimbursing the manufacturer for developing).
The present invention provides a solution to this problem. Like the prior art "MLS" series radio transceivers and the arrangement described in the commonly-assigned Ingham application, the present invention provides different transceiver front panel escutcheon plate assemblies for different transceiver feature configurations. Unlike past arrangements, however, the present invention does not require any electrical components to be provided within differently configured interchangeable escutcheon plate assemblies.
In accordance with one aspect of the present invention, the same basic transceiver unit is used for several different transceiver feature configurations. This basic transceiver unit typically may provide all of the (software controlled) features and functions of the "top of the line" transceiver feature configuration (and thus provides a superset of the features and functions provided by the other transceiver "models"). This basic transceiver also provides a mechanism for substantially irreversibly selecting a subset of the total features provided by the basic transceiver unit--this selection mechanism preferably being operable from outside of the transceiver case. Once made, the selection is preferably difficult or impossible to reverse--preventing a purchaser from defeating the selection in an attempt to enable additional transceiver functions.
In the preferred embodiment, for example, there are holes cut through the transceiver front panel in registry with associated underlying printed circuit board pathways. To irreversibly disable certain transceiver functions, it is necessary only to sever the pathways. Severing the pathways does not destroy hardware functionality in the preferred embodiment, but instead disables performance of certain portions of the transceiver microprocessor software programming implementing advanced or "optional" features.
As mentioned above, the feature selection mechanism provided by the present invention is preferably substantially irreversible. For example, a purchaser trying to form solder or other similar conductive bridges over the severed printed circuit board pathways in order to defeat the feature selection (and thus "upgrade" his transceiver to provide additional features without paying the additional associated purchase price to compensate the manufacturer for the development costs associated with those additional features) would probably find it necessary to disassemble and reassemble the transceiver (in all likelihood damaging certain components in the process).
These and other features and advantages of the present invention will be better and more completely understood by referring to the following detailed description of presently preferred exemplary embodiments in conjunction with the appended sheets of drawings, of which:
FIG. 1 is an elevated side view in perspective of a presently preferred exemplary embodiment of a digital radio transceiver in accordance with the present invention including an escutcheon plate assembly having a full-featured "SYSTEM" control configuration;
FIG. 2 is an exploded side perspective view of the escutcheon plate assembly shown in FIG. 1 showing how the assembly is mounted to the transceiver front panel;
FIGS. 3 and 4 are elevated front views in plan of escutcheonplate assemblies interchangeable with the escutcheon plate assembly shown in FIG. 1;
FIG. 5 is a front plan view of the transceiver shown in FIG. 1 with the escutcheon plate assembly removed to expose the transceiver case front panel;
FIG. 6 is a top plan view of an exemplary flexible printed wiring board (PWB) disposed within the FIG. 1 transceiver beneath the front panel exposed in the FIG. 5 view;
FIG. 7 is a schematic block diagram of an exemplary microprocessor-based circuit within the FIG. 1 transceiver;
FIGS. 8A and 8B are detailed schematic diagrams of an exemplary keypad scanning circuit portion of the circuit shown in FIG. 7; and
FIG. 9 is a flowchart of exemplary program control steps performed by the transceiver digital microprocessor shown in FIG. 7.